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    democritus and luecippus

    democritus and luecippus Democritus and Leucippus propose the idea of the atom, an indivisible particle that all matter is made of
  • Robert Boyle

    Robert Boyle
    24 Aug 1661 Robert Boyle published "The Sceptical Chymist" which was a treatise on the distinction between chemistry and alchemy. It also contained some of the earliest ideas of atoms, molecules, and chemical reaction marking the beginning of the history of modern chemistr
  • joseph black

    joseph black
    1 Jan 1754 Joseph Black isolated carbon dioxide, which he called "fixed air"
  • Antoine Laurent de Lavoisier

    Antoine Laurent de Lavoisier
    Lavoisier's Traité Élémentaire de Chimie (Elementary Treatise of Chemistry, 1789, translated into English by Robert Kerr) is considered to be the first modern chemical textbook. It contained a list of elements, or substances that could not be broken down further, which included oxygen, nitrogen, hydrogen, phosphorus, mercury, zinc, and sulfur. It also forms the basis for the modern list of elements. His list, however, also included light and caloric, which he believ
  • Lothar Meyer

    Lothar Meyer Unknown to Mendeleev, Lothar Meyer was also working on a periodic table. Although his work was published in 1864, and was done independently of Mendeleev, few historians regard him as an equal co-creator of the periodic table. For one thing, Meyer's table only included 28 elements. Furthermore, Meyer classified elements not by atomic weight, but by valence alone. Finally, Meyer never came to the idea of predicting new elements and correcting atomic weights. Only a few months aft
  • William Odling

    William Odling An English chemist, William Odling, also drew up a table that is remarkably similar to that of Mendeleev, in 1864. Odling overcame the tellurium-iodine problem and he even managed to get thallium, lead, mercury and platinum in the right groups – something that Mendeleev failed to do at his first attempt.
  • Dmitri Ivanovich Mendeleev

    Dmitri Ivanovich Mendeleev
    Dmitri Mendeleev, a Russian chemist, was the first scientist to make a periodic table much like the one we use today. Mendeleev arranged the elements in a table ordered by atomic mass, corresponding to relative molar mass as defined today. It is sometimes said that he played "chemical solitaire" on long train journeys using cards with various facts of known elements.[10] On March 6, 1869, a formal presentation was made to the Russian Chemical Society, entitled The Dep
  • Henry Moseley

    Henry Moseley In 1914 Henry Moseley found a relationship between an element's X-ray wavelength and its atomic number (Z), and therefore resequenced the table by nuclear charge rather than atomic weight. Before this discovery, atomic numbers were just sequential numbers based on an element's atomic weight. Moseley's discovery showed that atomic numbers had an experimentally measurable basis.
  • Glenn T. Seaborg

    Glenn T. Seaborg During his Manhattan Project research in 1943 Glenn T. Seaborg experienced unexpected difficulty isolating Americium (95) and Curium (96). He began wondering if these elements more properly belonged to a different series which would explain why the expected chemical properties of the new elements were different. In 1945, he went against the advice of colleagues and proposed a significant change to Mendeleev's table: the actinide series.
  • Johann Wolfgang Döbereiner

    Johann Wolfgang Döbereiner In 1817, Johann Wolfgang Döbereiner began to formulate one of the earliest attempts to classify the elements. In 1828 he found that some elements formed groups of three with related properties. He termed these groups "triads". Some triads classified by Döbereiner are:
    1.chlorine, bromine, and iodine
    2.calcium, strontium, and barium
    3.sulfur, selenium, and tellurium
    4.lithium, sodium, and potassium
  • Alexandre-Emile Béguyer de Chancourtois

    Alexandre-Emile Béguyer de Chancourtois Alexandre-Emile Béguyer de Chancourtois, a French geologist, was the first person to notice the periodicity of the elements — similar elements seem to occur at regular intervals when they are ordered by their atomic weights. He devised an early form of periodic table, which he called the telluric helix. With the elements arranged in a spiral on a cylinder by order of increasing atomic weight, de Chancourtois saw that elements with similar properties li